Have you worked on the car recently? Had this occur on mine after fitting some eibach springs, ended up stripping it all out again, splitting the plastic bearing collars, cleaning the old hardened grease out and re-applying fresh silicone grease which resolved the issue completely, also convinced the steering feels a bit lighter afterwards too.
The original grease had gone off and hardened up with age, they're getting on now and need a bit of TLC 🙂